Hello my lovely - firstly just wanted to say I'm sorry you are having a tough time. It's a drag sometimes isn't it! BUT, we press on!
I have had a few tests that I actually arranged through a local holistic fertility consultant, I had MTHFR, vitamin D, and all the thyroid tests (including the ones they don't always do under the NHS) so TSH, T4 and T3 and Reverse T3. I've also had progesterone done.
MTHFR was the more expensive one - that cost £180 Reverse T3 was £100 or so and the others weren't too bad at all.
I am also awaiting an appointment with Dr Quenby in Coventry who is one of the specialists I've heard rave reviews about but that is for repeat miscarriage so not the same possibly as what you are looking for? If you approach your local IVF clinic they often offer a lot of these additional tests but you kind of have to know what it is you want but hopefully the list above will help! Also, there is Dr Sherhata on Harley street. Some of them also do a 3D scan to see if there are any abnormalities of the uterus that a standard scan wont pick up, like a septum. I hope this helps!! Good luck xx